Turbomachine exhaust diffuser

ABSTRACT

Various embodiments include a turbomachine exhaust diffuser. In some embodiments, the turbomachine diffuser includes an inlet, an outlet opposing the inlet along a primary axis of the turbomachine diffuser, and a diffuser region between the inlet and the outlet. The diffuser region can include: a radially outer wall and a radially inner wall opposing the radially outer wall. The radially inner wall can include: a first section including a substantially uniform slope, and a second section continuous with the first section, the second section having a non-uniform slope.

FIELD OF THE INVENTION

The subject matter disclosed herein relates to turbomachines. Moreparticularly, aspects of the disclosure relate to turbomachine exhaustdiffusers.

BACKGROUND OF THE INVENTION

Turbomachine (e.g., steam turbine) designs generally include severalsections: a high pressure (HP) section, an intermediate pressure (IP)section and a low pressure (LP) section. The LP section includes aninlet, a plurality of stages, and an exhaust diffuser (or, exhaust hood)opposite the inlet. The diffuser is typically used to recover the staticpressure in the steam exiting the last stage bucket.

Conventionally, the diffuser is located axially downstream of the laststage bucket in the LP section, and provides a linear flow path for thesteam exiting the LP section. The conventional diffuser inherently hasspatial and geometric constraints which make it difficult to recover adesired amount of static pressure from the exiting steam. Thisconventional diffuser configuration can cause inefficiencies in thesteam turbine system.

BRIEF DESCRIPTION OF THE INVENTION

Various embodiments include a turbomachine exhaust diffuser. In someembodiments, the turbomachine diffuser includes an inlet, an outletopposing the inlet along a primary axis of the turbomachine diffuser,and a diffuser region between the inlet and the outlet. The diffuserregion can include: a radially outer wall and a radially inner wallopposing the radially outer wall. The radially inner wall can include: afirst section including a substantially uniform slope, and a secondsection continuous with the first section, the second section having anon-uniform slope.

A first aspect of the invention includes a turbomachine diffuserincluding: an inlet; an outlet opposing the inlet along a primary axisof the turbomachine diffuser; and a diffuser region between the inletand the outlet, the diffuser region including: a radially outer wall;and a radially inner wall opposing the radially outer wall, the radiallyinner wall having: a first section including a substantially uniformslope; and a second section continuous with the first section, thesecond section having a non-uniform slope.

A second aspect of the invention includes a turbomachine system having:a turbomachine having a low pressure (LP) section; and a turbomachinediffuser fluidly connected with an exhaust of the LP section, thediffuser including: an inlet; an outlet opposing the inlet along aprimary axis of the turbomachine diffuser; and a diffuser region betweenthe inlet and the outlet, the diffuser region including: a radiallyouter wall; and a radially inner wall opposing the radially outer wall,the radially inner wall having: a first section including asubstantially uniform slope; and a second section continuous with thefirst section, the second section having a non-uniform slope.

A third aspect of the invention includes a power plant system having: adynamoelectric machine; and a turbomachine system operably connectedwith the dynamoelectric machine, the turbomachine system including: aturbomachine having a low pressure (LP) section; and a turbomachinediffuser fluidly connected with an exhaust of the LP section, thediffuser including: an inlet; an outlet opposing the inlet along aprimary axis of the turbomachine diffuser; and a diffuser region betweenthe inlet and the outlet, the diffuser region including: a radiallyouter wall; and a radially inner wall opposing the radially outer wall,the radially inner wall having: a first section including asubstantially uniform slope; and a second section continuous with thefirst section, the second section having a non-uniform slope.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a side partial cut-away view of a turbomachine systemincluding a diffuser according to various embodiments of the invention.

FIG. 2 shows a schematic view a power plant system according to variousembodiments of the invention.

It is noted that the drawings of the invention are not necessarily toscale. The drawings are intended to depict only typical aspects of theinvention, and therefore should not be considered as limiting the scopeof the invention. In the drawings, like numbering represents likeelements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As noted, the subject matter disclosed herein relates to turbo-machines.More particularly, aspects of the disclosure relate to turbo-machineexhaust diffusers.

As described herein, steam turbine designs generally include severalsections: a high pressure (HP) section, an intermediate pressure (IP)section and a low pressure (LP) section. The LP section includes aninlet, a plurality of stages, and an exhaust diffuser (or, exhaust hood)opposite the inlet. The diffuser is typically used to recover the staticpressure in the steam exiting the last stage bucket. More particularly,as a working fluid such as steam flows from an area of relativelysmaller volume to an area of relatively greater volume, the kineticenergy of that fluid will decrease. This decrease in kinetic energycauses an increase in static pressure. Generally speaking, the moreeffective the diffuser is at reducing the kinetic energy of the fluid,the greater the diffuser is said to perform.

Conventionally, the diffuser is located axially downstream of the laststage bucket in the LP section, and provides a linear flow path for thesteam exiting the LP section. The conventional diffuser inherently hasspatial and geometric constraints which make it difficult to recover adesired amount of static pressure from the exiting steam. Thisconventional diffuser configuration can cause inefficiencies in thesteam turbine system.

Two conventional diffuser configurations are employed in order toincrease recovery of back pressure in steam traversing the diffuser.These approaches include: 1) The angled outer wall configuration; and 2)The “adjustable” inner wall configuration.

In the first scenario (angled outer wall), the radially outer wall ofthe diffuser is designed such that its angle is relatively steeprelative to the axis of the turbine. This provides for a greaterinternal volume in the diffuser, which allows for increased diffusionand consequently greater static pressure recovery. While this angledouter wall configuration can increase the static pressure recoveryrelative to a flat, planar outer wall configuration, the outer wallangle is limited by the physical dimensions of the diffuser.

In the second scenario (adjustable inner wall), the inner wall isconnected to an adjustment apparatus which can modify a position of theinner wall to effectively expand the volume within the diffuser forimproved static pressure recovery. However, this adjustment apparatuscan be expensive, and also consumes an undesirably large amount of spacewithin the diffuser.

In contrast to these conventional approaches, various embodiments of theinvention are directed toward a turbomachine diffuser with an inner wallthat includes a recess (or, divot). In particular embodiments of theinvention, a turbomachine diffuser is disclosed including: an inlet; anoutlet opposing the inlet along a primary axis of the turbomachinediffuser; and a diffuser region between the inlet and the outlet, thediffuser region including: a radially outer wall; and a radially innerwall opposing the radially outer wall, the radially inner wall having: afirst section including a substantially uniform slope; and a secondsection continuous with the first section, the second section having anon-uniform slope. It is understood that in various alternativeembodiments of the invention, the second section having the non-uniformslope can extend substantially an entire length of the diffuser 4.

FIG. 1 shows a side partial cut-away view of a turbomachine system 2including a diffuser 4 according to various embodiments of theinvention. As shown, the diffuser 4 can include an inlet 6, which can befluidly connected with a last stage 8 of a low pressure (LP) steamturbine 10 (further described herein). The last stage 8 of the LP steamturbine 10 includes a last stage bucket (LSB) 9, as is known in the art.The diffuser 4 can further include an outlet 12 opposing the inlet 6along a primary axis (A) of the diffuser 4 (which coincides with theprimary axis (A) of the turbomachine system 2. It is understood thatthis primary axis (A) denotes the axis of rotation of several componentswithin the turbomachine system 2, such as the LP steam turbine 10. It isfurther understood that as used herein, the terms “radial” or “radially”(e.g., radially inward, radially outward, etc.) refer to a locationalong the radial (R) axis, which is substantially perpendicular to theprimary axis (A) of the turbomachine system 2.

The diffuser 4 can further include a diffuser region 14 between theinlet 6 and the outlet 12. The diffuser region 14 can include asubstantially cavernous area where working fluid (e.g., steam) enteringthe diffuser 4 from the inlet 6 can expand (diffuse) before leaving thediffuser 4 at its outlet 12. The diffuser 4 in this case is an axialdiffuser, in that the diffusion region 14 generally expands incross-sectional area (and consequently, volume) from the axial inlet 6to the axial outlet 12.

As shown in FIG. 1, according to various embodiments of the invention(and in contrast to conventional approaches), the diffuser region 14 caninclude a radially outer wall 16 and a radially inner wall 18 opposingthe radially outer wall 16, where the radially inner wall 18 includes afirst section 20 including a substantially uniform slope and a secondsection 22 continuous with the first section 20, where the secondsection 22 has a non-uniform slope. That is, the second section 22 caninclude a recess 24 (or, divot) formed by two subsections 30, 32 havingdistinct slopes. In various embodiments of the invention, the firstsection 20 can have a substantially uniform positive slope, e.g., withrespect to the primary axis (A) of the turbomachine system 2.

More particularly, the second section 22 can include: a firstsub-section 30 with a positive slope relative to the primary axis (A) ofthe turbomachine system 2, and a second subsection 32 connected with thefirst subsection 30, where the second subsection 32 has a negative sloperelative to the primary axis (A) of the turbomachine system 2. In someembodiments, the second subsection 32 can be welded, brazed or otherwiseconnected with the first subsection 30 after formation of each of thefirst and second subsection 30, 32, respectively. However, in otherembodiments, the first subsection 30 and the second subsection 32 can beformed concurrently.

In various embodiments of the invention, the second section 22 of theradially inner wall 18 is located proximate the inlet 6. That is, thesecond section 22 (and particularly, the recess 24) is located within afirst axial half (or in some cases, a first axial third) of the diffuser4 as measured from the inlet 6. In particular embodiments, the secondsubsection 32 is located proximate (adjacent or near) the inlet 6. Incomparison with conventional diffusers, where recess 24 is locatedproximate the inlet 6 as in the various embodiments of the invention,the diffuser 4 is able to improve diffusion of the working fluid becauseof its larger volume proximate the LSB 9 (and the inlet 6). Thisenhanced diffusion causes a greater increase in static pressure recoveryin the diffuser 4 according to various embodiments of the invention,when compared with conventional approaches.

It is understood, however, that in various alternative embodiments, thefirst subsection 30 can extend a substantial length of the diffuser 4,occupying the space where first section 20 is depicted in FIG. 1 (shownin phantom as 30A). That is, first section 20 could be replaced by thefirst subsection 30A in some alternative embodiments.

As shown herein, the first subsection 30 and the second subsection 32can meet at an apex 34 (or, junction) (indicated by dashed circle forclarity of illustration) at the radial bottom of the radially inner wall18. In various embodiments of the invention, the first subsection 30 andthe second subsection 32 are separated an angle (β) of approximately 150degrees to approximately 179 degrees. In some particular embodiments,(β) can span between approximately 160-175 degrees, and in even moreparticular embodiments, (β) can span between approximately 165-170degrees.

It is understood that the diffuser 4 shown and described according tovarious embodiments of the invention is able to realize increasedefficiency over the conventional diffusers known in the art. Thisdiffuser 4 can realize an increase in static pressure recovery whencompared with the conventional diffusers, and can consequently increasethe efficiency of a turbomachine system (e.g., turbomachine system 2) inwhich the diffuser 4 operates.

FIG. 2 shows a schematic view of a power plant system 40 according tovarious embodiments of the invention. As shown, the power plant system40 can include a dynamoelectric machine 42, operably coupled to aturbomachine system 2 by a shaft 44. The dynamoelectric machine 42 caninclude a conventional electric generator, motor, etc., and theturbomachine system 2 can include components similarly shown anddescribed with reference to the turbine system 2 of FIG. 1. As is knownin the art, the dynamoelectric machine 42 is mechanically coupled withthe turbomachine system 2 (including, e.g., a gas turbine and/or steamturbine), and in some embodiments is designed to convert rotationalmotion from the turbomachine system 2 (e.g., from a rotating shaft) toelectrical energy for use in a variety of applications.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. It is further understood that theterms “front” and “back” are not intended to be limiting and areintended to be interchangeable where appropriate.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

We claim:
 1. A turbomachine diffuser comprising: an inlet; an outletopposing the inlet along a primary axis of the turbomachine diffuser;and a diffuser region between the inlet and the outlet, the diffuserregion including: a radially outer wall; and a radially inner wallopposing the radially outer wall, the radially inner wall having: afirst section including a substantially uniform slope; and a secondsection continuous with the first section, the second section having anon-uniform slope.
 2. The turbomachine diffuser of claim 1, wherein thesecond section includes a first subsection with a positive sloperelative to the primary axis of the turbomachine, and a secondsubsection connected with the first subsection, the second subsectionhaving a negative slope relative to the primary axis of theturbomachine.
 3. The turbomachine diffuser of claim 2, wherein thesecond subsection is located proximate the inlet.
 4. The turbomachinediffuser of claim 3, wherein the first subsection and the secondsubjection meet at an apex.
 5. The turbomachine diffuser of claim 3,wherein the first subsection and the second subsection are separated atan angle of approximately 150 to approximately 179 degrees.
 6. Theturbomachine diffuser of claim 1, wherein the second section forms arecess in the radially inner wall.
 7. The turbomachine diffuser of claim1, wherein the substantially uniform slope of the first section ispositive relative to the primary axis of the turbomachine.
 8. Aturbomachine system comprising: a turbomachine having a low pressure(LP) section; and a turbomachine diffuser fluidly connected with anexhaust of the LP section, the diffuser including: an inlet; an outletopposing the inlet along a primary axis of the turbomachine diffuser;and a diffuser region between the inlet and the outlet, the diffuserregion including: a radially outer wall; and a radially inner wallopposing the radially outer wall, the radially inner wall having: afirst section including a substantially uniform slope; and a secondsection continuous with the first section, the second section having anon-uniform slope.
 9. The turbomachine system of claim 8, wherein thesecond section includes a first subsection with a positive sloperelative to the primary axis of the turbomachine, and a secondsubsection connected with the first subsection, the second subsectionhaving a negative slope relative to the primary axis of theturbomachine.
 10. The turbomachine system of claim 9, wherein the firstsubsection and the second subjection meet at an apex.
 11. Theturbomachine system of claim 9, wherein the first subsection and thesecond subsection are separated at an angle of approximately 150 toapproximately 179 degrees.
 12. The turbomachine system of claim 8,wherein the second section forms a recess in the radially inner wall.13. The turbomachine system of claim 8, wherein the substantiallyuniform slope of the first section is positive relative to the primaryaxis of the turbomachine.
 14. A power plant system comprising: adynamoelectric machine; and a turbomachine system operably connectedwith the dynamoelectric machine, the turbomachine system including: aturbomachine having a low pressure (LP) section; and a turbomachinediffuser fluidly connected with an exhaust of the LP section, thediffuser including: an inlet; an outlet opposing the inlet along aprimary axis of the turbomachine diffuser; and a diffuser region betweenthe inlet and the outlet, the diffuser region including: a radiallyouter wall; and a radially inner wall opposing the radially outer wall,the radially inner wall having:  a first section including asubstantially uniform slope; and  a second section continuous with thefirst section, the second section having a non-uniform slope.
 15. Thepower plant system of claim 14, wherein the second section includes afirst subsection with a positive slope relative to the primary axis ofthe turbomachine, and a second subsection connected with the firstsubsection, the second subsection having a negative slope relative tothe primary axis of the turbomachine.
 16. The power plant system ofclaim 15, wherein the second subsection is located proximate the inlet.17. The power plant system of claim 15, wherein the first subsection andthe second subjection meet at an apex.
 18. The power plant system ofclaim 15, wherein the first subsection and the second subsection areseparated at an angle of approximately 150 to approximately 179 degrees.19. The power plant system of claim 14, wherein the second section formsa recess in the radially inner wall.
 20. The power plant system of claim14, wherein the substantially uniform slope of the first section ispositive relative to the primary axis of the turbomachine.